1. Field of the Invention
The present invention relates to an optoelectronic transceiver, and more particularly to an optoelectronic transceiver without xe2x80x9cTo-canxe2x80x9d or glass lenses.
2. Description of the Prior Art
An optoelectronic transceiver is used to transform an optical signal coming from an optical fiber connector to an electrical signal, or transform an electrical signal to an optical signal. A photo diode in the optoelectronic transceiver transforms the optical signal to the electrical signal and then sends the electrical signal to a processing circuit. A laser diode in the optoelectronic transceiver transforms the electrical signal coming from the processing circuit to the optical signal and then outputs the optical signal.
FIG. 1 shows a conventional optoelectronic transceiver 10. The optoelectronic transceiver 10 includes a front portion and a rear portion. The rear portion is composed of a large PCB (printed circuit board) 20, having a circuit (not shown) for processing the optical signal and the electrical signal, formed on its upper surface. There are 9 pins protruding from the lower surface of the large PCB 20. The front portion includes a laser diode 30 and a photo diode (not shown). The laser diode 30 is encapsulated into a xe2x80x9cTo-packagexe2x80x9d. As shown in the enlarged portion of FIG. 1, a laser diode chip 33 mounted on a small PCB 31 is covered with a metallic cup-shaped xe2x80x9cTo-canxe2x80x9d 37. A transparent window formed on the front terminal corresponds to the optical output path of the laser chip. A ball lens 38 or a glass lens is formed on the transparent window. Via the ball lens 38, the laser beam emitted by the laser diode chip 33 can be focused and projected. The laser diode 30 is inserted into a sleeve 35 so that the laser diode 30 can be aligned with a ferrule 61 of an optical fiber connector 60 connecting to an optical fiber 70. Since the configuration of the photo diode is similar to the laser diode, the detailed description is omitted.
Still referring to FIG. 1, in the laser diode 30, the laser diode chip 33 is electrically coupled to the circuit formed on the large PCB 20 via several external pins 39. The external pins 39 of the laser diode 30 are inserted into the through-holes of the large PCB 20 to form an electrical connection. It should be noted that in the conventional optoelectronic transceiver 10, parasitical capacitors and inductors lead to poor performance, such as poor transmission rate. The parasitical capacitors are mainly caused by the metallic cup-shaped xe2x80x9cTo-canxe2x80x9d 37 and the large PCB 20. The parasitical inductors mainly results from the external pins 39 because the conducting external pins 39 can be viewed as a inductor during high frequency, such as GHz.
The disadvantages of the conventional optoelectronic transceiver 10 further include the high manufacturing cost of the ball lens 38 and the fact that the configuration of the transceiver is unsuitable for small form factor (SFF). The reason a conventional transceiver is unsuitable for SFF is that the volume of the metallic cup-shaped xe2x80x9cTo-canxe2x80x9d 37 is too large compared to that of the laser diode chip 33. After being inserted into the sleeve 35, the volume is further increased. Accordingly, there is a strongly felt need for a novel optoelectronic transceiver for improving the transmission rate and reducing the manufacturing cost.
The present invention discloses an optoelectronic transceiver comprising a first PCB (printed circuit board), a transmitting device and a receiving device. The first PCB includes a first upper surface, a first lower surface and a plurality of pins. A circuit is formed on the first upper surface. The pins protrude from the first lower surface. The transmitting device is formed on the first PCB.
The transmitting device further includes a second PCB, a laser diode chip and a first sleeve. The second PCB further has a second upper surface and a second lower surface having leads formed thereon. The second PCB is electrically coupled to the first PCB. In an embodiment of the present invention, the laser diode chip is formed on the second upper surface of the second PCB. The semiconductor laser diode chip is electrically coupled to leads on the second lower surface. The laser diode chip responds to an electrical signal coming from the circuit on the first PCB to output an optical signal, such as a laser beam.
The first sleeve, transparent or opaque, has a first cambered surface and a second cambered surface formed at opposite terminals. The first sleeve covers the semiconductor laser diode chip and the second upper surface of the second PCB. The first cambered surface is aligned with the optical output path such that the laser beam emitted from the semiconductor laser diode chip can go straight forward along the first sleeve. That is, the first cambered surface serves as a lens. Additionally, the second cambered surface is aligned with the ferrule so as to focus the laser beam on the ferrule interposed between the first sleeve and the optical fiber connector. That is, the second cambered surface is used to focus.
A receiving device is also formed on the first PCB. The receiving device includes a third PCB, a photo diode chip and a second sleeve. The third PCB has a third upper surface and a third lower surface having leads formed thereon. The third PCB is electrically coupled to the first PCB. In an embodiment of the present invention, the photo diode chip is formed on the third upper surface of the third PCB. The photo diode chip is electrically coupled to leads on the third lower surface. The photo diode chip responds to an optical signal to send an electrical signal to the circuit on the first PCB for processing. The second cambered surface aligns the optical signal coming from the optical fiber to the second sleeve, and the first cambered surface focuses the optical signal on the photo diode chip. The optoelectronic transceiver in the present invention further includes a housing for covering the first PCB, the transmitting device and the receiving device.